//反向引用
/* let str1 = '<div>content</div>'
let str2 = '<p>content</p>'
let str3 = '<span>content</span>'
let str4 = '<div>content</div>'
let regexp = /\1<([a-z]+)>(.+)<\/\1>/;
 console.log(regexp.exec(str1));
console.log(regexp.exec(str2));
console.log(regexp.exec(str3)); 
console.log(regexp.exec(str4)); */

let a = "an4m5j6h2"
let re = /([a-z]+)(?:\d+)/
let res = re.exec(a)
console.log(res);
